Edit in JSFiddle

document.getElementById("uploadBtn").onchange = function () {
    document.getElementById("uploadFile").value = this.value;
};

<div class="fileUpload btn btn-primary">
    <span>Upload</span>
    <input id="uploadBtn" type="file" class="upload" />
</div>
<input id="uploadFile" placeholder="File Name here" disabled="disabled" />